/*
 * (C) 2009, Elephant Seven Hamburg Gmbh, 
 * Author: Detlev Wiese
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not 
 * use this file except in compliance with the License. You may obtain a copy 
 * of the License at
 *  
 *     http://www.apache.org/licenses/LICENSE-2.0 
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.se and its accompanying notice file is
 * included with the distribution. 
 */ 
package com.e7.streams;

import java.util.NoSuchElementException;

/**
 * <P>This class represents empty streams.</P>
 * <P>This class is a singleton, which allows access to its 
 * only instance throught the method {@link EmptyStream#soleInstance()}. 
 * </P>
 * @param <E> The type of the non-existing elements.
 */
public final class EmptyStream<E> extends AbstractStream<E> {
	
	private EmptyStream() {} 

	private static final EmptyStream<Object> soleInstance  = 
		new EmptyStream<Object>();
	
	/**
	 * Returns the only instance of this final class. 
	 * @param <E> The type of the non-existing elements
	 */
	@SuppressWarnings("unchecked")
	public static <E> EmptyStream<E> soleInstance() { 
		return (EmptyStream<E>)soleInstance; 
	}
	
	/**
	 * {@inheritDoc}
	 * <P>Note: the {@code EmptyStream}-instance will always return 
	 * {@code false}!</P>
	 * @return false
	 */
	public boolean hasNext() {
		return false;
	}

	/**
	 * {@inheritDoc}
	 * <P>Note: the {@code EmptyStream}-instance will always throw 
	 * a {@link java.util.NoSuchElementException}!</P>
	 */
	public E next() {
		throw new NoSuchElementException();
	}
}